(1) Field of the Invention
The present invention relates to the fabrication of integrated circuit devices, and more particularly, to a method of improving the deep contact processing window in the fabrication of integrated circuits.
(2) Description of the Prior Art
In the fabrication of integrated circuit devices with embedded memory, many interlevel dielectric layers exist between the substrate and the first metal lines. This makes for high aspect ratio contacts; that is, contact openings in which the ratio of height to width of the opening is greater than one. It is difficult to complete electrical contacts with high aspect ratios. Specifically, it is difficult to remove contaminants from the contact openings after etching. The contaminants prevent the formation of a good electrical contact. It is desired to find a method of forming good electrical contacts in high aspect ratio contact openings.
Silicidation has been used widely in the art. A refractory metal layer is deposited and then annealed. The underlying silicon reacts with the refractory metal layer to produce a silicide. U.S. Pat. No. 5,541,131 to Yoo et al shows a method of implanting silicon ions into a metal silicide layer as a source of silicon for silicidation during annealing. U.S. Pat. No. 5,236,865 to Sandhu et al teaches laser irradiation to simultaneously produce a silicide and activate dopants. U.S. Pat. No. 5,102,826 to Ohshima et al teaches implanting silicon ions into the substrate along with the dopant for forming junctions, depositing a titanium layer, then annealing for silicidation and activation where the implanted silicon ions suppress consumption of silicon in the substrate during silicidation. U.S. Pat. No. 4,954,214 to Ho teaches implanting silicon ions through openings in a molybdenum mask to act as seed material for selective deposition of tungsten.